Photographic processes for producing multicolor images



May 31, 1949. w. H. RYANI ETAL 2,471,547

PHOTOGRAPHIC PROCESS FOR PRODUCING MULTICOLOR IMAGES May 31 1949- y w.H. RYAN l-:T Al. 2,471,547

` PHOTOGRAPHIC PROCESS FOR PRODUCING MULTICOLOR IMAGES Filed Feb. 24,1947 2 SheebS-Sheet 2 Patented May 31A, 1949 PHOTOGRAPHIC PROCESSES FORPRODUC- ING MULTICOLOR IMAGES William H. Ryan and Vivian K. Walworth,Cambridge, Mass., assignors to Polaroid Corporation, Cambridge, Mass., acorporation of Delaware Application February 24, 1947, Serial No.730,274

3 Claims.

This invention relates to color photography and more particularly hasreference to processes for forming multicolor images, especiallyprocesses involving the sequential formation of a multiplicity of dyecomponent images in a single emulsion layer and to improvements in suchprocesses.

Objects of the invention are to provide novel and simplified processesfor forming multicolor images as well as processes of this characterwhich are readily controllable and which may be indefinitely repeatedwith uniform results and also to provide processes designed for multiplecopying of multicolor images. Other objects of the invention reside inthe provision of processes involving the sequential formation of dyecomponent images by successive preferential exposures of a single layeremulsion through different color records followed by successivetreatments leading to the formation of a multiplicity of dye images inthe layer and including practices for equalizing differences in thelight-sensitivity characteristics throughout the emulsion during thevarious stages of processing whereby the emulsion is in a substantiallyuni- `form image receptive condition for the sequential formation ofeach dye component image; and to the provision of processes of thisnature wherein developed silver images useful in the formation of dyecomponent images are rehalogenated to light-sensitive silver halide bytreatment which Will have substantially no effect upon or cause noimpairment of dyes used in the processes of the invention.

, Still further objects of our invention are the provision of colorphotographic processes wherein dye component images are formed insequence in a silver halide emulsion layer from images derived from thesequential exposure of the layer and wherein light-sensitive silverhalide is sequentially re-formed in the exposed portions of the layerand the sensitivity of the silver halide in the unexposed portions ofthe layer is equalized with respect to the sensitivity of the re-formedsilver halide; and particularly processes of such character wherein thesensitivity equalization is effected through the controlled uniformexposure of the layer at some stage of processing prior to exposureleading to the formation of a second dye component image in the layerand wherein the layer, without development of latent image formed bysuch uniform exposure is treated with an oxidizing agent which iscapable of destroying latent image without substantially affecting thedye of any component image contained in the layer or wherein the layerimmediately following the uniform exposure is treated with suchoxidizing agent and a halide having the same halogen element as that ofthe unexposed silver halide and which in combination with the oxidizingagent will react with silver and form silver halide which is developablesubstantially only upon exposure to light and which is the same halideas the previously unexposed halide while having substantially similarlight-sensitivity characteristics therewith.

The invention accordingly comprises the processes involving the severalsteps and the relation and the order of one or more of such steps withrespect to each of the others which are exemplified in the followingdetailed disclosures, and the scope of the application of which will beindicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings wherein:

Figure 1 shows characteristic density-log relative exposure curves, oneof which results from the exposure and development of a photographicemulsion layer with a color-forming developer in the ordinary manner togive magenta dye and the others of which each represents a separateportion of a similar emulsion layer which has been subjected to thespecial processing and treatment of the present invention, including acontrolled uniform exposure, whereby to form magenta dye in theseportions of the emulsion layer; and

Fig. 2 shows density-log relative exposure curves for magenta dye formedin separate portions of an emulsion layer like that of Fig. 1 bypractices of the present invention but with the omission of a controlleduniform exposure.

In processes of color photography in which silver images, useful in theformation of dye images, are formed in sequence in a single emulsionlayer of silver halide, it becomes necessary to restore the silver whichcomprises the silver images to silver halide which is not spontaneouslydelevopable. Silver halide which is reformed from silver in generalpossesses a lower sensitivity to light than does the original unexposedsilver halide in such a layer. To obtain good color rendition it isnecessary in such processes to adjust the sensitivity differences or .toequalize the sensitivity of the re-formed halide and the portions of thesilver halide emulsion which are not previously developed in order torender the emulsion suitably receptive to color component images formedafter any exposure and development step in such processes.

Several methods have been provided for accomplishing these effects, theprincipal one of the prior art involving an exposure sufficient toexpose substantially all of the silver halide in the layer to light,developing the halide to silver and re-forming in both the image andnonimage portions light-sensitive silver halide which has essentiallyuniform light-sensitivity characteristics. The technique of thejust-describedH character, While giving acceptable results, requiresadditional chemical solutions and washes, thereby adding to the time,expense and intricacy ofthe color process. i

An important feature of this invention resides in the fact that noadditional solutions, Washes or time-consuming operations, for example,special silver development treatment, are required to effect theadjustment of sensitivity differences in the image and nommage portionsof the emulsion layer and that the techniques herein employed may beconveniently fitted into substantially any multicolor process involvingrehalogenation of developed silver.

In a copending application of William I-. Ryan for Color photographicprocesses, Serial No. 721,546, nled January 11, 1947, there has been setforth a color process which involves the successive formation of colorcomponent images in a single emulsion layer by color-forming developmentand through practices which rehalogena'te or restore the developedsilver image to silver halide in a proper condition for the reception ofsequentially formed images. In the process of the just-mentionedapplication Serial No, 721,546, the reformation of the silver halidefrom developed silver is effected through action of a rehalogenatingcomposition or compositions which, in addition to converting silver tosilver halide, effect the adjustment of inertial difference between theimage and nonimage portions of the emulsion and also substantiallydestroy latent image. By

nonimage portion, We mean that portion of an emulsion which, in thesequential formation of a setr of color or dye component images adaptedAto form a multicolor image, has not been exposed to a color recordprevious to its exposure for the printing of the second-formed colorcomponent image in the series and by image portion We mean any portionof the emulsion containing a dye image, or a dye image and a silverimage or a dye image and silver halide re-formed from silver.

The practice of this invention presents an improvement in the practicesset forth in the aforementioned application Serial No. 721,546 in thatit renders the image and nonimage portions of the emulsion substantiallysimilar not only in inertia but also in gamma. This improvement isconveniently brought about through the employment of controlled flashingtechnique used in conjunction vvith the special rehalogenating treatmentset forth in application Serial No. 721,546. Furthermore, the controlledflashing practice permits special adjustment in the characteristics ofthe nonimage portion of an emulsion by variation in the duration andintensity of the flash whereby a range of development gammas may beobtained.

To this end the present invention preferably renders an emulsion layersubstantially uniformly light-sensitive while re-forming substantiallynonspontaneously developable silver halide in an exposed and developedsilver or image portion thereof by subjecting the emulsion to controlledflashing followed by subjecting the flashed emulsion without developmentto the action of a rehalogenatng composition or compositions whichcontain an oxidizing agent capable of oxidizing metallic silver tosilver ion, substantially destroying latent image and depressing thesensitivity of unexposed silver halide. In fact, it may be said that anoxidizing agent which will destroy latent image will also depress thesensitivity of unexposed silver halide. oxidizing agents and othermaterials used with the present invention also possess the property ofbeing substantially inactive With respect to dyes used in forming dyeimages and especially with respect to photographically useful dyesresulting from Colorforming development of latent silver halide, wherebythe dyes are substantially unharmed or unimpaired.

It is also important to note that a further feature of our processresides in the fact that the treatment time in the rehalogenatingcomposition necessary to effect the desired adjustment of inertiabecomes relatively shorter and less critical than when theheretofore-mentioned controlled uniform exposure is not employed.

As indicated, the practices set forth herein are concerned With theformation, in a single emulsion layer, of one or more multicolor images,through the formation of a set of suitably registered or overlapping dyeor color images for each multicolor image in the layer. The invention isuseful for multiple `copying of multicolor positives, originals, printsand reproductions, especially through the use of suitably prepared colorrecords as, for example, color separation negatives, and is particularlyadapted for the copying of motion picture lm. At the same time, theprocesses are suited for use with cut film or with roll and may beemployed in the formation of either positive or negative images.

Conventional photographic lms and papers comprising a single emulsion onan opaque or transparent support are suitable for use with the inventionto form transparencies or reflection prints. A commercially available lmWell adapted in the practices of the invention for use as ravv Stock isordinary release positive film such as is used :for ordinary black andwhite motion pictures, this being one of the cheapest motion picture lmsnovv produced. Films having an emulsion layer on each side of a support,i. e., duplitized film may also be employed. When duplitized ilm isused, one or more color image components are formed in each emulsionlayer ofthe film. A silver bromide or si-lver chloride emulsion isemployed with nlm of the character just described and the terms silverhalide and "silver halides are used generically herein to refer to bothof these light-sensitive substances. Primarily for the sake ofconvenience and simplicity of processing, the emulsion employedpreferably contains only one silver halide and not a mixture thereof.

rlhe reha-logenating practice whereby silver halide is re-formed fromsilver is carried out by treating an emulsion layer with an aqueoussolution of an oxidizing agent and With the approp-riate halide ion, theoxidizing agent being capable of oxidizing the metallic silver to silverion substantially Without affecting dyes formed bycolor-formingdevelopment and the halide ion reacting with silver ion to form thedesired silver halide'. Alternatively, this practice may compriseoxidizing metallic silver to silver ion with an oxidizing agent of thecharacter described, and converting silver ion to an insoluble silversalt which is transformable to the desired silver halide by reactionwith the appropriate halide ion.

Preferred oxidizing agents are cupric ion, ferrie ion and ferri-cyanideion, and compounds providing'the same may be found among inorganic andorganic compounds comprising cupric chloride, cupric bromide, cupricsulfate, cupric nitrate, ferric chloride, ferric bromide, ferricammonium citrate, ferric oxalate, sodium ferricyanide, potassiumferricyanide, ammonium ferricyanide and mixtures thereof.

The halide ion which provides the desired silver halide is furnished bya water soluble halide which may be included in the compositioncontaining the oxidizing agent or a developed emulsion may be firsttreated only with an oxidizer and after formation of the insolublesilver salt may then be treated with the desired halide as. for example,a solution of potassium bromide or potassium chloride.

One example of a suitable rehalogenating composition comprises Potassiumbromide g 200 Cupric chloride g 35 Water to make l 1 Immersion of adeveloped emulsion in the above composition for about three minutes atabout 68 F. will usually be satisfactory for rehalogenating purposes. Inthe composition just given potassium bromide which furnishes the desiredhalide ion is included with the oxidizing agent. If desired, treatmentof the emulsion may be carried out with separate solutions of oxidizingagent and halide.

In the alternative practice, previously mentioned, an anion other thanthe desired halide is employed to the end of converting silver ion to aninsoluble silver salt which, through an ion exchange reaction with anappropriate halide in aqueous solution is transformed to the desiredsilver halide. An example of this rehalogenating treatment, which may becarried out in two steps, comprises first immersing a developed emulsioncontaining a silver image and a dye image in Solution I Potassiumferricyanide g Sodium hydroxide g 1 Water to make cc 100 followed byimmersion in Solution II Potassium bromide g 10 Water to make cc 100Treatments in both Solutions I and II are carried out for about fiveminutes at about 68 F. The sodium hydroxide in Solution I speeds up thereaction resulting in the formation of insoluble silver ferrocyanidewhich reacts with potassium bromide to give silver bromide. 1f desired,the potassium bromide may be added to Solution I and rehalogenationeffected in a single s ep.

As another example of the formation of an insoluble silver salt, adeveloped silver image may be oxidized with cupric'nitrate and treatedwith sodium sulfate to form insoluble silver sulfate which upon reactionwith an appropriate halide will give the desired silver halide.

It isimportant to note that in all rehalogenating treatments of theinvention, the reaction products other than silver halide which resultupon the formation of that substance are of a soluble character wherebytheir removal is readily facilitated.

When rehalogenating silver to silver chloride, equivalent amounts ofpotassium chloride may be substituted for the potassium bromide ineither of the compositions specifically given by way of illustration.

Halides besides potassium bromide and potassium chloride which areuseful with the processes of the invention comprise ammonium chloride,ammonium bromide, sodium chloride, sodium bromide and other solublemetal halides.

Commercially available photographic films vary tremendously in theirinitial light sensitivity. Some are highly sensitized with dyes, forexample, while others rely solely on the light sensitivity of thehalides themselves. Many films contain mixtures of chloride and bromideor bromide and iodide which enhance the light sensitivity of theemulsion. Commercial lms are also normally subjected to ripening andwashing operations in the course of their manufacture which increase thesensitivity of the halide. Variations of the character just describedwill therefore tend to make silver halide re-formed from silver not onlydifferently sensitive from the original halide of the emulsion but,generally speaking, less sensitive. lease positive film is about tentimes more sensitive than silver halide re-formed in accordance with thepractices of ths invention.

Due to the just-noted fact that most commercial i'llms have a highersensitivity than reformed silver halide, the depressant eiect onunexposed silver halide by the rehalogenating compositions used by theinvention becomes important. As an illustration of this depressanteffect, when release positive emulsion is treated with one of therehalogenating compositions, hereinafter set forth, the inertia of theemulsion may be increased approximately 1 log Ev unit, and if desiredunder special conditions may be increased further. With fasteremulsions, the effect of the compositions of this invention will also beto reduce sensitivity.

Specifically, with commercially available positive films, thedesensitizing action of these rehalogenating compositions is suflicientto bring the sensitivity of the unprinted portions of the emulsion layerwithin the same range of sensitivity as that of re-formed silver halide,so that multicolor reproductions which are within accepted commercialtolerances of color rendition are obtained. In general, it is consideredthat an error of approximately ten per cent or less in the density ofany color component is acceptable. As a specific example, colortolerances within this limit have been consistently obtained with theuse of the heretofore-mentioned release positive lm.

The present invention is concerned with a more perfect color renditionthan that just mentioned and with one whereby the error in the densityof any color .component is of a relatively small order. As indicated,this is accomplished by procedure which not only permits an adjustmentof inertial difference between the image and nonimage portions of theemulsion but also permits an adjustment of gamma in these portions. Whensuch practice is employed, a color For example, the previously mentionedre-` acuer? z balance is obtainedc whereby multicolor images are formedwhich closely reproduce the original colors they are intended torepresent.

It has been brought out that the invention is intended for use with anycolor-forming process wherein a multiplicity of dye component images areformed in a single emulsion layer and in which silver useful in theformation of dye images is restored to silver halide. In thisconnection, consider an emulsion layer containing light-sensitive silverhalide, a color image component comprising a dye and a silver imagewhich is coextensive with the color image component, the only previouslyexposed portion of the emulsion being that portion in which the silverimage and dye image are located. At such a stage, our process proceedsby subjecting the layer to a ash exposure which is controlled as toduration and intensity, following which, and without development, thelayer is subjected to the rehalogenating treatment heretofore described.The effect of this procedure is to impart to the layer a sensitivitywhich closely approaches equality in the various portions thereof.

The exposure to be given by the controlled flash will depend upon anumber of factors. For example, exposure will vary in accordance withsuch factors as the inertia of the initial emulsion, that is to say, theinertia in the nonimage portions thereof, and also with the developmentgamma desired with reference to subsequent development after therehalogenating treatment.

For a specific example of controlled flashing, reference is made to theheretofore-mentioned release positive emulsion with which verysatisfactory results have been obtained when it is subjected tocontrolled flashing carried out by moving the film at a rate of thirtyfeet per minute past a conventional fifteen-watt incandescent bulblocated at about two inches from the film or by holding the lmstationary and exposing it for one second to a conventionalone-hundredwatt incandescent bulb located at about twentyfour inchesfrom the film.

Following the controlled flash exposure and the rehalogenating of silverto silver halide, the layer is in a condition to receive a further dyeimage component which is formed by suitably exposing the layer, forexample through a color separation record, and then treating the layerwith one of the rehalogenating compositions to again restore it to acondition receptive for the formation of additional images.

Alternatively, instead of performing the controlled dashing andrehalogenating steps immediately following the formation of the firstdye image and when the layer also contains a silver image, if desired,the film may be flashed prior to the formation of any image andsubjected to the rehalogenating practices. This latter procedure, aswill be apparent, adds additional steps to the photographic processing.It is important to observe, however, that the controlled flash techniqueneed be carried out only once in the practice of this invention for thesequential formation in a single layer of a multiplicity of dye images.

At this point it may be well to repeat that one effect of the controlledflashing and the rehalogena-ting treatment is to destroy latent imageand to restore silver to a light-sensitive nonspontaneously developablecondition while lowering or depressing the overall sensitivity of theemulsion or increasing its inertia. A second effect of controlledflashing and rehalogenating il. 't

(ft rfa results 'in a changein the slope of the characteristic curve ofthe emulsion whereby to equalize sensitivity throughout the emulsion sothat the gamma of all parts of a subsequently exposed and developedimage will be substantially the same regardless of the portion of theemulsion upon which the image may be printed.

That the two just-mentioned effects take place is evidenced from thecharacteristic curves shown in the various views of the drawings andwhich represent characteristic curves of release positive emulsionresulting from various treatments of the same, certain of the curvesincluding treatment by flashing and rehalogenating silver to silverhalide.

In Fig. 1, four curves I0, Il, i2, and I4, are disclosed. Curve i0represents the characteristics of fresh release positive emulsion whichhas been exposed to a gray scale, developed in a magenta,colorforrningdeveloper, subjected to rehalogenating treatment whereby to convertsilver associated with magenta dye to silver halide, fixed, washed anddried. The curves Il, l2- and i4 represent a typical range of conditionswhich would be expected to occur in the ordinary course of forming amulticolor image in release positive film by the use of controlledflashing in conjunction with the practices set forth in the previouslymentioned application Serial No. '721,546 including steps resulting inthe formation of the second color image component in such process.

With a multicolor image being formed by successive exposure of a singlelayer emulsion through color separation negatives, it is preferable toform the successive dye images in the order of the transparency of thedyes to the region of the spectrum in which the emulsion is particularlysensitive. When an essentially ultravioletancl blue-sensitive emulsionsuch as silver chloride or silver bromide emulsion is employed, cyan dyewill be preferably first formed, followed by formation of magenta dye,which in turn is followed by the formation of yellow dye when threecolor components are provided.

Curves Il, I2 and i4 specifically illustrate magenta dye density inthree different portions of release positive emulsion. In obtaining datafor curves H, I2 and Ill one portion of fresh release positive emulsionwas given no exposure while two other portions were given gradedmeasured exposures. The portion of the emulsion represented by curve ilwas given no rst exposure. The portion represented by curve l2 was rstexposed to a gray scale, that is, given a graded exposure varying fromno exposure to an exposure equivalent to that required to produce fulldensity in the dye image which is normally first formed in that portionof the emulsion. The portion of the emulsion represented by curve I4 wasgiven a uniform exposure equivalent to that requiredV to produce fulldensity in the dye image which is normally first formed in that portion.

The two portions of the emulsion containing latent image were thendeveloped in a black and. white developer approximating thecharacteristics typical of a cyan color-forming developer in that itprovides silver of equivalent density to silver resulting from cyancolor-forming development. For example, a color-forming developer couldbe employed without the use of a coupler. Color-forming development ofthese two portions of the emulsion was not employed since the presenceof a dye image would make it dicult to obtain accu-rate measurements ofthe characteristic curves of subsequently formed images. lt isl to benoted that the two portions subjected to the iust-described developmentmay be said to have a rst image formed therein.

Following the just-described development, the two portions of theemulsion having silver therein were treated in a stop bath, washed,` andsub- Vjected to a controlled flash exposure followed by treatment in arehalogenating composition prior to any further development, after whichthese portions were washed, treated in a clearing bath, washed anddried. At this sta-ge the two portions of the emulsion subjected to theforegoing treatment contained unexposed silver halide in the nonimagepart thereof and silver halide which was re-formed from silver in theimage or the previously exposed part thereof.

The third portion of the emulsion, namely that portion which was givenno iirst exposure and development, and which is illustrated withreference to curve II, was given the controlled flash exposure of thisinvention and without development subjected` to the action of theoxidizing agent of one of the rehalogenating compositions previouslydisclosed by immersing that portion of the emulsion in such arehalogenating composition, following which this portion of the emulsioncontaining no image was treated in a clearing bath, washed and dried.

Magenta dye was then formed in all three portions of the releasepositive emulsion by exposing each portion to a gray scale anddeveloping in a magenta developer. Silver associated with the magentadye was removed by rehalogenating treatment to form silver halide andeach of the three emulsion portions were iixed, washed and dried.

The dye densities in the three portions of the emulsion which wererespectively given no exposure and graded exposures and the combinediiashing and rehalogenating treatment were measured by a photoelectricinstrument whereby to obtain data for the curves I I, I2 and I4.Similarly, the dye density in the portion of the lm which was notsubjected to the practices of this invention but was merely exposed anddeveloped with the magenta color-forming developer was measured by aphotoelectric instrument for the plotting of the curve II). It is to bekept in mind that the densities given in curves I, II, I2 and I4, andfor that matter in all curves shown in the drawings, were measured by aphotoelectric instrument and that the measured densities do notcorrespond with visual densities.

A study of the curves in Fig. 1 clearly shows by the horizontaldisplacement of curves II, I2 and I4 from the curve I0 that the inertiaof the emulsion is increased following the flashing and rehalogenatingpractices discolsed herein, it being kept in mind that curve Irepresents the characteristics of fresh emulsion which was exposed to agray scale and which contained only a magenta image but which was notsubjected to the processing of this invention. This increase asdisclosed is approximately equal to 1 log E unit.

Furthermore, vcurves. Il, I2 and Iii show the second effect ofcontrolled flashing and rehalogenating practice, namely, theequalization of sensitivity th-roughout the emulsion whereby the gammaof all parts of any image exposed and developed after the first dyecomponent image will be substantially the same regardless of thatportion of the emulsion upon which such subsequent image is printed. Inthis regard it is to be noted that curves II, I2 and I4 are of the samerelative shape and lie closely parallel to eachother, from which fact itbecomes evident that density disparities vvare reduced -to negligibledifferences' between portions of the emulsion representing the initialsilver halide and Iportions in which a silver image has been formed andsubsequently rehalogenated to silver halide and which coupled with theincrease in inertia renders the emulsion substantially uniformlyreceptive for the formation .fof subsequentl ,dye images whereby topermit faithful color rendition.

As further. evidence of the improvements effected by this inventionwhereby color balance for multicolor images may be obtained, referenceis made to Fig. 2 Vand to the curves I5 and I6 `thereof representativeof characteristic curves for release positive emulsion, one portion ofwhich, represented by curve I5, has been subjected to processing such asthat resulting in the 'curve II but without the controlled Iiashing stepof the present invention, the portion represented by the curve I5 havingno first exposure image formed therein. On the other hand, the curve I6of Fig. 2 was obtained by the treatment of a portion of the emulsionthrough processing practices similar to those outlined inconnection withcurve I4 of Fig. 1 and also without employment of the controlled flashprocedure but with the formation of a first image of uniform fulldensity therein.

While curves I5 and I6 indicate that an increase of inertia is obtainedthrough the use of the oxidizing agent of the rehalogenatingcomposition, they show that there is some disparity in the gammas of theunexposed and the exposed portions of the emulsion. This is apparentfrom the fact that curves I5 and I6 are not closely parallel to eachother and that the over-all separation between them is considerablywider vthan between the curves II, I2 and I4 of Fig. 1.

ing ashing and rehalogenating practices in a process for the sequentialformation of color component images whereby to produce a multicolorimage.

The practices herein set forth broadly constitutean improvement of'color processes which sequentially form dye component images in avsingle-layered emulsion and which involve reforming silver halide fromsilver useful in the formation of the dye images, In this regard thecontrolled ashing Vand rehalogenating techniques may be fitted into anycolor process of the character heretofore noted. For example, controllediiash exposure and rehalogenating practices such as we have disclosedmay be used 1n processes wherein a silver image printed from a colorrecord is converted to a dye mordant and after the mordanting ofy a dyethereto is reacted to form silver or a silver salt from which desiredsilver halide-may be re-formed by treatment in a rehalogenatingcomposition or compositions such as are described herein. Our iiashingand rehalogenating practices are especially adapted for use with and areconveniently fitted into the color'photographic process of applicationSerial No. 721,546, which makes use yof sequential color-formingdevelopment. Accordingly, and by way of completely describing ourinvention, a specific process involving sequential color-formingdevelopment and leading to the formation of `three-color or dyecomponent sans@ Iilm- The steps in .oortelet processing are as ofollows:

Sodium carbonate, des -g-- 25 Sodium sulte vg 1 p-Diethylaminoanilinemonohydrochlorid g A-.6 `Potassium bromide g-- 0.42,4-dichloro-1-naphthol g-- 1 Acetone -ml-- 100 Water to make l 1 Theresult of this development is to form ya silver image and a cyan dyeimage exposed in the portion of the emulsion layer of the film.

3. Immerse for one minute in stop bath having the following formula:

Alternatively, other types of stop baths may be employed, such, `forexample, -as bisulte Aor buffer solutions with va pH of-4.5 -to 6 forlimited positive motion --picture vfilm, exposure may be made by aconventional fifteen-Watt incandes- .cent bulb located at labout twoinches from rthe lm which'is moved pastfthe bulb at the-rate of thirtyfeet per minute or, `when the film is held stationary,exposure'isfor'one second to a con- `ventional one-hundred:wattYincandescent bulb located at twenty-four `inches from the Afilm.

6. Treat lfor three lminutes in the following solution:

Step 6 is the :rehalogenating `treatment previously described and .aresult of carrying out this operation is to.re-formsilvery "halideinrany exposed por-tion of the film and following such treatment theemulsion layer contains silver halide throughout Aand the componentimage formed of cyan dye, thesilverhalide `being'substantially uniformlysensitive and developable only upon exposure to. light.

7- Wash for three minutes.

The purpose .or this, washing step. is to remove any residual, iWoserating composition, including oxidizing nt, arid any Solublereaction products or the. r .Losenating treat.- ment. If desired,priorv'o trashing, the lm may be subjected to a clearing. hath.l forexample a clearing bath comprising bisulte, the treatment in such a bathbeingfor `a limited time whereby to leave anydye componentimage presentin the nlm substantially unaffected'.

8. Dry.

9. Expose lm to magenta printer negative (green separation negative)proper register.

10. Develop Vforthree andv a half minutes,

magenta -color developer having the V-following formula:

Sodiumcarbonate des g 12.5 'Sodium sulte rg- 6 p-Diethylamino anilinemonohydrochloride .g- I .f. Potassium Vbromide g .25`ApNitrophenylacetonitrile g-- .25 f Acetone gl25 vWater .to -make l 1Following exposureanddevelopment to provide the magenta image, theemulsion layer contains light-sensitive halidathe cyan component image,the magenta component image and also developed silver.

11 through 15. Steps following this development Vare the same as thosefollowing ythe cyan color development with the omission orthe-controlled flashing of .step 5 but including the practices of steps3, 4, 6, .7 and 8.

Following reconversion of silver to silver :halide b y step `13 in theprocess, the emulsionlayer contains light-sensitive silver halidethroughout, .the cyan component image and the magenta component image,but no silver.

16. Expose lm to yellowprinter negative (blue separation negative) in`suitable register.

17. Develop in yellow color developer lhaving .the following formula:

Sodium carbonate, des fg-- `Sodium sulte g 5 p-Diethylaminoahilinemonohydrochloride e-- 3 Potassium bromide g '2 `Ethyl acetoacetate -ml20 Acetone ml-- Water to make l 1 Following the yellow development, theemulsion layer contains light-sensitive Vsilver halide, the cyancomponent image, the magenta component image, silver and the yellowcomponent image.

18 through 20. The next three Vsteps are the same as those following thecyan color development' with the omission :of the controlled flashing ofstep 5 but including the practices of steps v3, 4 and 6.

The effect of rehalogenating in step 20 is to convert silver tolight-sensitive silver halide lto the end that the emulsion layercontains lightsensitive silver halide throughout and cyan, magenta andyellow dye components which together form at least one multicolor image.

After step 19, that is, washing after treatment in a stop bath such asAthat illustrated in step v, the silver in the lm Amay be removed ordestroyed by any practice which does not harm the dye images. Aconvenient manner of accomplishing this is to rehalogehate the silver tosilver halide which leaves the .entire emulsion layer in a conditionwherein substantially all substances except the dye images may beremoved by conventional xing baths followed by washing and drying.Alternatively, Iafter step 20 a sil-ver sound track or other auxiliarysilver image may be formed in the emulsion layer of the lm by proceduressuch as those, set forth in the copending application of William I-I.Ryan, for Color photographic processes for producing multicolor imagesand associated auxiliary images andproducts thereof, Serial No. 721,548,yfiled lJanuary 11J 1947.

As regards to` dyes. formed by color-forming development, our inventionintends. to make use of any photographoally useful. dye `of `this`char-- acteiz Typical examples of dyes which may be employed arerepresented by those used in Kodachrome, Ansco Color, and Kodacolorprocesses. It is important to observe that dyes resulting fromcolor-forming development are in general more highly subject to attackby oxidizing agents, acids, and other reagents and substances than aremordant dyes useful for photographic purposes.

Nondichroic dyes and dichroic dyes may be formed by color developmentand both classes are included within the scope of this invention.Dichroic dyes are especially suited for the formation oflight-polarizing images and are useful in the practice of vectography. Adichroic dye as distinguished from a nondichroic dye will form adichroic sorption complex with a molecularly oriented plastic and willdifferentially absorb incident light when incorporated in the plastic.Suitable plastic materials in the form of linear high polymers arehereinafter named.

As specific examples of nondichroic dyes resulting from the colordevelopment of exposed silver halide mention may be made of aaomethine,indoaniline, indophenol, indanthrene andl indamine dyes. These may beformed by so-called primary developers which directly form coloredcompounds in the development of latent silver halide to silver as wellas by so-called secondary developers which when oxidized and reactedwith a coupler will form colored compounds.

VMany dyes which display suitable dichroism and which are of appropriatecolor may be found among the azo dyes and these may be formed throughythe use of developers from the class of organic compounds known ashydrazines. The primary aromatic hydrazines provide both primary andsecondary developers especially suited for this purpose and as examplesthereof mention may be made of phenylhydrazine; bromo andchloronaphthylhydrazines; tolylhydrazines; nitrophenylhydrazines; brornoand chlorophenylhydrazines; a-naphthylhydrazine; p,p'-diphenylhydrazine; methoxyphenylhydrazines; p-carybethoxyphenylhydrazine; andthe like. Generally speaking, wherever couplers are employed withhydrazines which form secondary developers, compounds corresponding tothe couplers useful in forming nondichroic dyes may be employed.

In the practice of this invention, the carrier in which the emulsion isdispersed may be formed of any suitable hydrophilic material. Materialsof this nature comprise gelatin and transparent, hydrophilic, highmolecular weight, linear polymers which may have their moleculesoriented and which form a dichroic sorption complex with certain organicdyes, as well as other materials suitable as emulsion carriers.

If the molecules of a high linear polymer are oriented and an image isformed therein comprising a dichroic dye, the image will belightpolarizing in character and the invention is intended to includethis concept within its scope. As specific examples of suitablelong-chain, hydrophilic, transparent plastics which may have theirmolecules oriented, mention may be made of polyvinyl alcohol,polyhydroxy alkane, partially hydrolyzed polyvinyl acetals and polyvinylalcoho esters, amylose, regenerated cellulose, and suitably preparedpolyamides or nylon-type plastics.

Gelatin and polyvinyl alcohol may be named as preferred carriermaterials.

Although the term halogenating is GllStOmarily used in organic chemistryin a narrower sense than it is employed herein, it is employed to meanthe step of forming silver halide from silver and rehalogenating is usedthroughout the specification and claims to define the step of formingsilver halide from silver which has at some previous stage been derivedfrom a silver halide.

While having its principal usefulness in the field of three-colorphotography, our process should not be construed as limited to theformation of three-color images and sound track, as heretoforedescribed, The practices of the invention may be used for the formationof two-color pictures with or without sound track; for the formation ofso-called anaglyph pictures for stereoscopic purposes; for the formationof light-polarizing images which may be employed for stereoscopicpurposes; or in general for the formation of any plurality of images ina single emulsion layer for any purpose.

Since certain changes may be made in the above process without departingfrom the scope of the invention herein involved, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. A process of color photography which comprises exposing an emulsionlayer containing light-sensitive material comprising at least one silverhalide selected from the class consisting 0f silver bromide and silverchloride and forming therein a latent image representative of a colorcomponent of a multicolor image; developing said latent image with acolor-forming developer which forms a dye image and a silver image insaid layer; giving the layer a controlled uniform exposure to light;without development of latent image created by said uniform exposure,treating said layer by subjecting the layer to the action of only onesoluble halide which is reactable with silver ion to form silver halideand which is selected from the class of halides consisting of solublebromides and soluble chlorides, and an oxidizing agent which issubstantially inactive with respect to image dye and which in thepresence of the soluble halide selected from said class of solublehalides, possesses the properties of effecting formation from silver ofsilver halide havlng a halogen element which is the same as that of saidsoluble halide, of destroying latent image, of reducing the sensitivityof unexposed silver halide and of forming reaction products other thansaid silver halide which are soluble whereby the light-sensitivematerial of said layer essentially comprises silver halide having thesame halogen element as said soluble halide and possesses substantiallyuniform but lower sensitivity than the light-sensitive material of saidlayer prior to any exposure thereof; forming in the layer in registerwith said already-formed dye image at least one other latent imagerepresentative of another color component of said multicolor image anddeveloping the last-mentioned latent image with a color-formingdeveloper which forms in said layer a silver image and a dye imagehaving a color dilferent from that of said rst-mentioned dye image; andwhen multicolor image formation is concluded removing substantially allsilver and silver salts from said layer.

2. A process of color photography which comprises exposing an emulsionlayer containing substantially only silver bromide to a color componentimage; developing said layer with a colorl forming developer which formsa silver image and a dye image in said layer; exposing the layersubstantially uniformly to light; withoutdevelopment of latent imagecreated by said uniform exposure, treating said layer by subjecting thelayer to the action of a soluble bromide which is reactable with silverion to form silver bromide and an oxidizing agent which is substantiallyinactive with respect to image dye and which in the presence oi saidsoluble bromide possesses the properties of forming silver bromide fromsilver, of destroying latent image, of reducing the sensitivity ofunexposed silver bromide and of forming reaction products other than.silver bromide which are soluble, whereby the light-sensitive materialof said layer essentially comprises silver bromide and possessessubstantially uniform but lower sensitivity than thelightfsensitivematerial ci said layer prior to any exposure thereof;ex.- posing said layer to a second colorV component image in registerwith the dye image in said layer; developing the layer With acolor-forming developer which forms in saidlayer a silver image and adye image having a color dilerent from that of said inst-mentioned dyeimage; Without any exposure of the layer subjecting said layer,including the lastmentioned silver image, said dye images and residualsilver bromide, to the action of said oxidizing agent and said solublebromide; exposing said layer to a third color component image inregister with the dye images in said layer; developing the layer with acolor forming developer which forms. a silver image and a dye imagehaving a color different from that of said rstand second-mentioned dyeimages; and substantially freeing the layer of silver and silver saltsremaining therein.

3. A process of color photography which comprises exposing an emulsionlayer containingl substantially only silver chloride to a colorcomponent image; developing said layer with a colorforming developerwhich forms a silver image and a dye image in said layer; exposingthe'layer substantially uniformly to light; Without development oflatent image created by said uniform ex- 16 posure, treating said layerby subjecting the layer to the action of a soluble chloride which isreactable with silver ion to form silver chloride and an oxidizing agentwhich is substantially inactive With respect to image dye and which inthe presence of said soluble chloride possesses the lproperties offorming silver chloride from silver, of destroying latent image, ofreducing the sensitivity of unexposed silver chloride and of formingreaction products other than silver chloride which are soluble, wherebythe light-sensitive material of said layer essentially comprises silverchloride and possesses substantially uniform but lower sensitivity thanthe light-sensitive material of said layer prior to any exposurethereof; exposing said layer to a second color component image inregister with the dye image in said layer; developing the layer with acolor-forming developer which forms in said layer a silver image and adye image having a color diferent from that of said first-mentioned dyeimage; without any exposure of the layer subjecting said layer,including the last-mentioned silver image, said dye images and residualsilver chloride, to the action of said oxidizing agent and said solublechloride; exposing said layer to a third color component image inregister with the dye images in said layer; developing the layer with acolorforming developer which forms a silver image anda dye image havinga color different from that of said firstand second-mentioned dyeimages; and substantially freeing the layer of silver and silver saltsremaining therein. WILLIAM H. RYAN. VIVIAN K. WALWORTH.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,976,301 Seymour et al Oct. 9,1934 2,210,905 Eggert et al. Aug. 13, 1940 2,244,589 Yanket June 3, 1941

